Add a new migration to make sure that fast forward column exists in projects table

db/migrate/20150827121444_add_fast_forward_option_to_project.rb

@@ -12,6 +12,8 @@ class AddFastForwardOptionToProject < ActiveRecord::Migration
   end
   def down
-    remove_column(:projects, :merge_requests_ff_only_enabled)
+    if column_exists?(:projects, :merge_requests_ff_only_enabled)
+      remove_column(:projects, :merge_requests_ff_only_enabled)
+    end
   end
 end

db/migrate/20171004121444_make_sure_fast_forward_option_exists.rb

+# rubocop:disable all
+class MakeSureFastForwardOptionExists < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    # We had to fix the migration db/migrate/20150827121444_add_fast_forward_option_to_project.rb
+    # And this is why it's possible that someone has ran the migrations but does
+    # not have the merge_requests_ff_only_enabled column. This migration makes sure it will
+    # be added
+    unless column_exists?(:projects, :merge_requests_ff_only_enabled)
+      add_column_with_default(:projects, :merge_requests_ff_only_enabled, :boolean, default: false)
+    end
+  end
+
+  def down
+    if column_exists?(:projects, :merge_requests_ff_only_enabled)
+      remove_column(:projects, :merge_requests_ff_only_enabled)
+    end
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
-ActiveRecord::Schema.define(version: 20170928100231) do
+ActiveRecord::Schema.define(version: 20171004121444) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"